1. Field of Invention
The present invention relates generally to a method and apparatus for applying an endless annular tread to a tire casing, and more specifically, to a method and apparatus for transferring a tread onto a tire casing.
2. Description of the Related Art
Annular treads are commonly used in truck tire retreading. Such an annular tread is disclosed in U.S. Pat. No. 3,815,651 to Neal. Annular treads as disclosed in the Neal patent have a relaxed diameter less than the inflated diameter of the tire casing. These annular treads must be stretched radially outwardly to be fitted over the tire casing. Machinery directed to this process has been disclosed in U.S. Pat. No. 4,957,575 to Robert A. Chronin et al. Chronin disclosed a method of clamping an annular tread to a pneumatic tire casing wherein the casing was mounted on a wheel and the tread on a tread expander assembly. The tread expander assembly is moved along a line coincident with or parallel to the wheel rotational axis. The tread expander assembly has a means expandable outwardly and retractable inwardly along the radial direction of the wheel for selectively stretching a tread by radially outward displacement of the tread at a number of spaced points on the radially inner side of the tread. By actuating the tread expander, the tread is expanded to a size sufficient to circumferentially surround the casing. Chronin then teaches the step of moving the tread toward the casing to a position where the stretched, annular tread circumferentially surrounds and is centered on the casing. Chronin then teaches that by encircling the casing and the stretched tread with a clamping assembly, the assembly having a plurality of space clamping means and, using such assembly and without rotating the casing or the tread relative to such clamping assembly clamping the stretched tread to the casing by sequentially or simultaneously pressing on the radially outward most surface of the tread at spaced clamping points. Each clamping point is located between points where the stretching forces apply. Chronin then unclamps the stretched tread at the clamping points and transfers the annular tread from the tread expander assembly onto the casing by moving the tread expander assembly axially away from the casing. The Chronin device requires that the undertread surface or radially inner surface of the tread and the radially outer surface of the casing are contacted by the stretching means of the tread expander assembly. The application of a precured tread to a casing many times involves an adhesive coating to be applied at the mating surfaces of the casing and the tread. The prior art devices are in direct contact with these mating surface areas and inherently must contact these adhesives upon transferring the tread to the casing.
The present invention will accurately center the tread on the casing while insuring that the tread stays firmly centered on the casing during the transfer of the tread to the casing without requiring any physical contact with the radially inner surface of the tread or the radially outward surface of the casing in the region where the two components are to be joined.